I'm trying to write an HttpModule to run on our SharePoint farm - essentially it will check whether the user is authenticated and if they are it will validate some info against another database and potentially redirect the user to sign a variety of usage agreements.

Whenever I enable the module in the web.config I'm finding that SharePoint has issues rendering the page - it's almost like the CSS is not getting loaded as the page is devoid of any styling.

As a test I've even tried an empty module - i.e. an empty init block so it's not even hooking up any code to any events and the same issue arises. At this point it's an empty class that just implements IHttpModule so it's not even my dodgy coding causing the issue!

The module is in a class library that I've dropped in to the bin folder of the application it needs to run against. In the web.config of the app I've simply added an entry as below:

<modules runAllManagedModulesForAllRequests="true">
  ... (default stuff ommitted)
  <add name="SharePointAUP" type="SPModules.SharePointAUP" />
</modules>

I must be missing something really obvious here as I've done exactly the same as every sample I've found and yet I'm getting this strange behaviour. Is there something extra I need to do to get SharePoint to play nice with a custom module?